It has long been known to make amine oxides by reaction of tertiary amines with aqueous hydrogen peroxide with or without a co-solvent. Catalysts reported to promote the reaction are octacyanomolybdate or iron salts (U.S. Pat. No. 4,565,891), carbon dioxide (U.S. Pat. No. 4,247,480), alkali metal polyphosphate and bicarbonate (U.S. Pat. No. 3,333,000), sodium salt of ethylenediamine tetraacetic acid (U.S. Pat. No. 3,432,555) and salicylic acid (Chem. Abst. 102(18) 151229 g).
Nitrosamines are formed as minor by-products in the conventional preparation of tert-amine oxides using aqueous hydrogen peroxide. Although the amount of nitrosamine is very small, on the order of parts per billion (ppb), this small amount renders the amine oxide unsuitable in many applications that involve human contact. This is because nitrosamines are reported to be carcinogenic and/or mutagenic. Amine oxides have properties that would make them very useful in shampoo, hair conditioners, dish and laundry detergent, fabric softeners and the like. Hence a need exists for a method for making tert-amine oxides in high conversion and yield and at a fast reaction rate and at the same time producing a tert-amine oxide product that has reduced levels of nitrosamines. The present invention provides such a process.